Adjustable gas distribution means for multiple tube electrical precipitators



May 1, 1945. H. J. WHITE 2,374,715

ADJUSTABLE GAS DISTRIBUTION MEANS FOR MULTIPLE TUBE ELECTRICALPRECIPITATORS Filed Jan. 20, 1943 2 Sheets-Sheetl ADJUSTABLE GASDISTRIBUTION MEANS FOR MULTIPLE TUBE ELECTRICAL PREC TATORS Filed Jan.20, 3 2 Sheets-Sheet 2 y 1945- H. .1. WHITE 2,374,715

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Hal-r KE/L Patented May 1, 1945 ADJUSTABLE GAS DISTRIBUTION MEANS FORMULTIPLE TUBE LELECTR'ICAL PRE- CIPITATORS Harry J. White, Cambridge,Mass., assignor to Research Corporation, New York, N. Y., a corporationof New Yorl;

Application January 20, 1943, Serial No. 473,008

3 Claims.

This invention relates generally to apparatus for electricalprecipitation of suspended particles from gases, and more particularlyto means for controlling the distribution of gas flow in each of theparallel gas tubes of a multiple tube electrical precipitator, a generalobject of the invention being the provision of conveniently adjustablemeans for establishing uniformity of gas flow in the tubes of such aprecipitator for any total rate of gas flow throughout a relatively widerange. The invention has particular application to and utility in atwo-stage precipitator of the water film type, such as shown in my priorPatent N 0. 2,192,249, and is herein described particularly in thatconnection, though it also has application to and is described inconnection with precipitators which do not employ water films.

In multiple tube precipitators of the class to which the inventionappertains, either with 'or without water films, the gas is distributedfrom a header to the inlet ends of a plurality of parallel, cylindricgas conduits, usually and preferably vertically disposed, though notnecessarily so. Within each of these conduits is a concentrichigh-tension electrode, while the conduits provide collecting electrodesurfaces opposing the high-tension electrodes, onto which suspendedparticles charged by the action of the discharging electrode areprecipitated. In Water film precipitators, these collecting electrodesurfaces are each supplied with a flowing water film, which is designedto collect and carry off the precipitated material.

In the preferred, two-stage type of precipitator, the high-tensionelectrode includes a discharging section, typically in the'formof a finewire, and a non-discharging section, of materially increased radius ofcurvature, the non-discharging section following the discharging sectionin the direction of gas flow. The expression discharging section ordischarging electrode will be understood to designate an electrode thatfacilitates corona discharge therefrom because it has a configurationthat establishes asufficiently high potential gradient at or near itssurface to create corona, discharge before there is disruptive dischargeor sparkover. The expression nondischarging section or non-dischargingelectrode will be understood to designate an electrode that minimizes orprevents corona dis-- charge therefrom because it has a configurationthat establishes a sufficiently low field concentration at or near thesurface to suppress corona discharge at, elevated potentials lower thanthe voltage required for disruptive discharge or sparkover. For thispurpose, a non-discharging electrode is usually one of extended surfacearea, substantially free from sharp corners or other parts'ofsharpsurface curvature at all portions which are located with n theelectric field, so as substantially to avoid ionization or coronadischarge at that electrode.

Uniformity of action and high efliciency in precipitators of the classesmentioned depend upon the avoidance of excessive turbulence of the gasflowing through the conduits, and upon the establishment ofsubstantially uniform gas distribution in the regioncf the high-tensionelectrodes. It is particularly important to avoid nonuniformity of gasdistribution and excessive turbulence in water film types of apparatus,for the reason that excess; ely turbulent gas flow exerts a disruptiveefiect on the water film, breaking loose droplets of Water and causingsparking between the electrodes. ,I have found that excessive turbulenceand non-uniformity of distribution of the gas within the conduitsfrequently arises from non-uniform or unsymmetrical entrance of the gasinto the intake ends of the conduits, and are contributed to by gassurges resulting from sudden changes in pressure. A conduit whose inletend comprises simply the unobstructed end of a round tube, of course,provides uniform distribution of the gas. However, it is usuallydesirable to provide some form of damper means located at the inlet endsof the conduits for regulating the rates of inflow into the conduits.and such damper means as invariably constructed heretofore have causedunsym metrical gas entry, and consequent non-uniform gas distributionand turbulence in the conduits.

It is, therefore, a primary object of the present invention to providesimple, inexpensive damper means at the inlet ends of the conduits, soformed as to assure symmetrical distribution of the gas at point ofentry, and therefore decreased turbulence and increased uniformity ofgas distribution within the conduits.

A further object of the invention is the provision of a simple andinexpensive gas control means at the inlet ends of the gas conduits forconveniently adjusting the individual rates of gas flow, and a stillfurther object is the provision of novel and improved gas control meansfor securing uniform or any other desired adjustment and distribution ofgas fiow among the several conduits, as well as enabling the inletorifice of one or more tubes to be entirely closed.

These objects are accomplished in accordance with the invention by theprovision of damper width at the inlet ends of-the several conduits.

For example, I may employ in spaced relation to the inlet end of eachconduit a damper element in the form of a disc, cone, cap or the like,mounted coaxially with the end of the conduit, so as to cooperatetherewith lar inlet orifice. This disc, cone, cap or the like isarranged for axial adjustment movement whereby the width of the orificeand therefore the rate of gas inflow may be regulated and is preferablymovable entirely into engagement with the inlet end of the conduit,whereby the orifice may be entirely closed and the corresponding conduittaken out of action, if desired. The inlet orifice is symmetrical withrespect'to the axis of the conduit in all positions of adjustment,

with the result that the inflow of gas is uniform and symmetrical aboutsaid axis. The adjustment thus not only permits close control of therate of gas flow in a simple and inexpensive manner, but the symmetry ofthe inlet orifice assures uniformity of distribution of the gas in theconduit with respect to its central axis in all positions of adjustment.By then spacing the high-tension electrode a fairly substantial distancefrom the inlet end of the conduit, the gas is given an opportunity toequalize its distribution radially of the conduit, and is not onlyuniformly distributed about the axis of the conduit, but issubstantially uniformly distributed across it-i. e., radially of theconduit-by the time it reaches the high-tension electrode, and the waterfilm region opposite it, if the apparatus be of the water film type. Atthe same time, the damper element largely prevents sudden gas surges oreddies fromentering the conduit. The individual gas control means at theinlet ends of the several conduits permit the accomplishment of anydesired distribution of the total gas flow among the several conduits,uniform or otherwise, and permit ready compensation for any tendency forany, of the conduits to take in more or less gas than'do the others.

Various additional objects and corresponding accomplishments of theinvention will appear and be described in the course of the followingdetailed description of certain present illustrative embodimentsthereof, reference vfor this purpose being had to the accompanyingdrawings in which:

Fig. 1 is a vertical medial section of the lower portion of a water-filmtype of precipitator equipped with the improvements of the, presentinvention, it being understood that the upper portion of theprecipitator, not shown herein, may be, for instance, of the type shownin my prior Patent No. 2,192,249; v

Fig, 2 is a perspective showing in some detail the illustrative flowcontrol means of Fig. 1;

Fig. 3 is a detail cross-section on line 33 of Fig.

Fig. 4 is a view similar to Fig. 1 but showing theinvention'incorporated in a'screen pocket electrode type ofprecipitator;

Fig. 5 is a transverse section taken as indicated by line 5-5 of Fig. 4;

Fig. 6 is a bottom view of a modified form of damper cone indicating theoptional use of perforations in the damper element;

Fig. 7 is a vertical section showing'the optional perforated type ofdamper cone, and

Fig. 8 is a vertical medial section of a further modified type of gascontrol means.

Fig. 1 shows the lower portion of a two-stage in the definition of anannuwet-electrode precipitator comprising a plurality of preferablyvertical gas conduits ID, of substantially circular cross-section,arranged in parallel, all the conduits being supplied with gas to betreated from a header II at the bottom of the apparatus; a detailedconsideration of the upper portion of the apparatus not being essentialto an understanding of the present invention, no illustration thereof isincluded herein, though reference may be had to my aforesaid Patent No.2,192,249 for a detailed description of a complete precipitator of thetype intended.

The apparatus is encased in a cylindrical housing l2, preferablyconstructed of sheet metal, a header plate l3 extending across theinterior of the housing defining the upper side of the aforementionedheader l I. This plate I3 is here shown as slanting, for a purpose whichwill presently appear, though this arrangement is not essential.

A gas inlet duct l5 opens inside header ll, preferably just below thehigh side of header plate 13, and a water outlet l6 mounted in the wallof housing 12 just below the lowermost edge of slanting plate vl3 servesas a drain for water descending from above and caught by plate 13.

Each of gas conduits In, in the form of the invention here chosen forillustrative purposes, comprises an upper tubular electrode I8,maintained at ground potential, and a lower gas inlet tube I9 extendingthrough and mounted in plate l3, tube i9 beingof lesser diameter thantubular electrode l8 and its upper end-being received partially withinthe lower end portion of the latter, with a small annular space 20 beingprovided therebetween. This space 20 is preserved by spacing lugs 20awelded to the outside of tube I9. As here shown, the tube i9 is mountedon header plate I3 by means of a flange 2| welded to the tube andclamped by means of bolts 22 between a gasket 23, which bears againstthe header plate, and a clamp ring 24. The lower ends of the inlet tubes:9 depend from header plate 13 to a level preferably well below gasinlet duct l5.

Disposed within and co-axially of each of the tubular electrode membersI8 is a complementary central or high-tension electrode assembly 30, thelower part of which comprises a fine wire discharge electrode 3!adapted, in cooperation with the surrounding tubular electrodes, tocreate an ionizing field, and the upper part of which comprises anextended surface electrode 32 of relal tively large diameter adapted, incooperation with from the lower ends of the electrodes l8 via anthatpart of tubular electrode I8 which surrounds it, to provide a staticelectric precipitating field free from corona discharge. The lower endof the central high-tension electrode assembly terminates somewhat abovethe lower end of the tubular electrode member I8, as shown.

It will be understood that the inner surfaces of the several tubularelectrodes i 8 are supplied from above with water films, which dischargenular spaces 20, and are caught by sloping header plate .13, to bedischarged finally by way of water outlet l6.

Each of gas inlet tubes l9 comprises two pipe sections 35 and 36 havingflanges 31 and 38, respectively, on their adjacent ends. The annular rim39a of a spider 39 is received between flanges 31 and 8, and theassembly is clampedtogether by means of bolts 40. Bolted to anddepending from the hub 4| of each of spiders 39 is a vertical dampersupporting rod 42, which is thus co-axial with the gas inlet tube [9.perforated damper disc 43, of approximately the A centrally diameter ofthe gas inlet tube, is mounted on each of rods 42 and supported by a nut44 which is screwed onto the threaded lower section 45 of the rod. Thisdisc 43, in cooperation with the annular lower end of tube section 35,defines an annular gas inlet orifice, whose width, or height, isdetermined by the position of nut 44 on supporting rod 42.

The annular inlet orifice provided by the damper disc is entirelysymmetrical in all positions of adjustment, and assures uniform andsymmetrical entry of the'gas into the gas inlet tube with respect to thecentral axis of the latter. The distribution of the gas at point ofentry is thus uniform. with respect to the axis of the inlet tube. Asthe gas rises in the tube, its distribution across the section of thetube tends to become equalized, and by the time it has reached theregion of the tubular electrode l8 and high-tension wire 3! itsdistribution across the conduit is substantially uniform. The consequentreduction in swirling and turbulence reduces to a minimum the tendencyfor the gas flow to. disrupt the water films on the insides of thetubular electrodes. Surges of gas into the lower ends of the gas inlettubes, and consequent eddies and turbulence from that cause, are alsominimized by the presence of the damper disc, which acts as a shield toguard against unrestricted entry of such gas surges. Very close controlof the rates of flow through the individual tubes, as well as of thedistribution among the several tubes, is secured by individualadjustment of the vertical positions of the damper discs 43 by means ofthe adjusting nuts 44. And,

if desired, the discs 43 may be set up against the ends of any inlettubes which it may be desired to take out of action. Attention isdirected'to the preferred location of the gas inlet duct 15 well abovethe lower inlet ends of the tubes l8, this arrangement preventing thelateral gas current entering via duct I5 from disturbing the uniformflow of the gas into the annular inlet orifices.

Figs. 4 and 5 show the invention applied to a multiple gas conduitprecipitator which is of the screen pocket electrodetype, and also showthe damper means in a modified form. In this embodiment, the header I laformed in the bottom of housing l2a is defined at the top by a hoppershaped structure 50 comprising walls 5i sloping downwardly from the sidewall of housing In to a central discharge outlet 52 leading to dischargescrew conveyor 53. Gas inlet duct l5a opens inside header I I a, asindicated.

Vertical gas conduits la comprise upper ,tubular electrode members I8a,similar to the tubular electrodes l8 of the precipitator of Fig. 1, andlower gas inlet tubes 190. which extend through and are mounted in thewalls tubes [9a being of lesser diameter than tubular electrodes l8a andtheir upper ends being received partially, and with annular clearance,within lower end portions of electrodes I8a, and being joined at theirupper ends to tubular screen members l4 which are spaced from electrodemembers l8a and form therewith annular pockets for the collection ofprecipitated material. The tubular electrodes 18a contain co-axiallypositioned hightension electrodes a. The annular clearance spacesbetween the gas inlet tubes Na and the tubular electrodes l8a aredesigned to pass the collected dust as it. falls from the insidesurfaces of electrodes l8a, this dust being caught by hopper 58, andremoved by conveyor 53. Any material which may fall from screen membersI4 down through the inside of inlet tubes 19a may be removed from headerIla through door 49.

. Each of gas inlet tubes Isa is supported by a flange 55 welded to itnear its lowerend, this flange being clamped, by means of bolts 55,between clamp ring 51 and the annular-flange 58 on the lower end of asupporting sleeve 58 which depends from and is welded to wall 5|, agasket 50 being here shown as placed between flange 55 and the flange 58on sleeve 58.

Mounted in each of gas inlet tubes l8a is a spider 55, .to the hub 55 ofwhich is bolted the upper end of damper supporting rod 61, the latterdepending to a point somewhat below the lower end of tube l9a, asillustrated. While the supporting rod 61 might carry a disc-type damperelement, of the kind illustrated in Fig. 1, I here show a modifiedcone-shaped damper element 58. This cone-shaped damper element 58 has acentral sleeve 59 slidably mounted on supporting rod 51, a downwardlydiverging conical wall I0 connected with the upper end of sleeve 69, and

radial webs H joining sleeve 59 with wall 10. The lower end 'of sleeve69 is shown provided with a collar 12 in which is mounted a clamp screw13 adapted to be set up against supporting rod 51 to secure the damperelement in any position of vertical adjustment on rod 81.

This form of the invention operates in a mannor substantially similar tothat of the form previously described, the cone-shaped damper elementagain defining a symmetrical annular inlet or'fice of adjustable height,which in all positions of adjustment assures symmetrical and uniformflow of the gas from the header into inlet tubes ISa, and thereforeuniform distribution of the gas with reference to the central axis ofthe gas conduits, as well as substantially uniform distribution of thegas across the conduits bythe time it reaches the region of thehightension electrodes.

Figs. 6 and 7 show a modified form of conical damper element, in whichthe conical wall 10 is provided with a plurality of perforations I5.

. These perforations 15 are distributed uniformly about the axis of thecone so that the gas entering inlet pipe l9a through them will have auniform distribution about the axis of the inlet pipe, and thus serve toprovide additional or increased symmetrically distributed gas inflow.Such perforations may be, of course incorporated in other forms of thedamper element than the conical form illustrated in these figures.

Fig. 8 shows a further modification, in which the damper element is inthe form of a cup 88,

the bottom wall 8| of which is spacedfrom and cooperated with the lower'end of gas inlet tube |9a in the definition of an annular gas inletori. fice, and the side wall 82 of which extends upwardly above thelower end of tube 19a. The bottom 8| of cup is centrally perforated topass supporting rod 61, and is provided with a collar 83 carrying aclamp screw 84 adapted to vbe set up against suporting rod 61 to securethe cup in any position of vertical adjustment on rod 51. The gas entersby way of the annular space provided between the side wall '82 of thecup and the lower end portion of tube I911, thence passing inwardlythrough the annular orifice between the lower end of tube I91; and thebottom 8| of the cup, and then upwardly within the tube I5a, all asindicated by the arrows in Fig. 8. It will be evident that the damper ofFig. 8 is similar to the damper 43 of Fig. 1, with the exception of theaddition of side wall 82. This added side wall 82 i has the advantagethat it acts as a shield against any lateral gas currents which mayprevail inside header Ila, thus preventing such ciu'rents frominterfering with the uniform and symmetrical inflow of gas into thelower ends of tubes [9a. It will, of course, be understood that thedamper element shown in Fig. 8, as well as any of the modiiied forms ofdamper element, disclosed. may be employed in connection with any of theforms of precipitator illustratively disclosed herein, or any other towhich the invention is broadly applicable.

It will be understood that the drawings and 3 description are merelyillustrative of and not restrictive 'of the invention, and that variouschanges in design, structure and-arrangement may be made withoutdeparting from the spirit and scope of the invention or of the appendedclaims.

I claim:

1. In an electrical precipitator having a vertical gas conduit embodyingan upper tubular electrode surrounding a co-axially positioned ihigh-tension electrode, and a co-axially positioned lower gas inlet tubeof lesser diameter than said tubular electrode 'and annularly spacedtherewithin to provide an annular opening for discharge of precipitatedmaterial from the upper tubular-electrodes: a damper member spaced belowthe lower end of said gas inlet tube, and means adjustably supportingsaid damper member for movement toward and from the inlet end of saidinlet tube along the vertical longitudinal axis of saidv tube, saiddamper member being shaped to define with said inlet end 01' said inlettube a symmetrical annular inlet orifice.

- 2. In an electrica1 preclpitator having a vertical gas conduitembodying an upper tubular electrode surounding a co-axially positionedhightension electrode, and a co-axially positioned lower gas inlet, tubeof lesser diameter than said tubular electrode and annularly spacedtherewithin to provide an annular opening for discharge of precipitatedmaterialfrom the upper tubular electrodes: a damper disc spaced belowthe lower end of said gas inlet tube, and supporting means for saiddamper disc embodying upper tubular electrodes: a damper cone spacedbelowrthe lower end of said gas inlet tube, and supporting means forsaid damper cone comprising a rod mounted co-axially of said gas inlettube and projecting from the inlet end thereof, said cone having acentral perforation adapted to receive said rod, and being supportablein various positions of longitudinal adjustment on said rod.

HARRY. J. WHITE.

